Shaped articles of cellulose phenylthiourethane and method of producing them



Dec. 27, 1955 A. L. ALLEWELT 2,728,630

SHAPED ARTICLES OF CELLULOSE PHENYLTHIOURETHANE AND METHOD OF PRODUCING THEM 2 Sheets-Sheet 1 Filed March 30, 1950 EXTENSlB/L/TY TENS/LE STRENGTH DRY TENS/LE STRENGTH WET [DH 0F BA TH is a: 'c.

INVENTOR. Al? THUR L. ALLEWELT BA 7H TEMP.

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Dec. 27, 1955 A. 1.. ALLEWELT SHAPED ARTICLES OF CELLULOSE PHENYLTHIOURETHANE AND METHOD OF PRODUCING THEM 2 Sheets-Sheet 2 Filed March 30, 1950 BATH TEMP.

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INVENTOR. ARTHUR L. ALLEWELT BY a ATTORNEY.

United States Patent SHAPED ARTICLES 0F CELLULOSE PHENYL- THIOURETHANE AND METHOD OF PRO- DUCING THEM Arthur L. Allewelt, West Chester, Pa., assignor to American Viscose Corporation, Wilmington, DeL, a corporation of Delaware Application March 30, 1950, Serial No. 152,954

6 Claims. (CI. 18-54) This invention relates to shaped articles such as fibers, films, tubes, rods, and other articles comprlsing a cellulose-phenylthiourethane and to a new process for producing them. More particularly, it relates to cellulosea of imparting to the cellulose certain chemical properties which are similar to the properties of wool, such as swelling characteristics and an afiinity for wool type dyestuifs. However, the physical properties, including the extensibility (by which is meant elongation at break), of fibers formed from the cellulose-phenylthiourethane in conventional coagulating baths, are not satisfactory. Either the dry extensibility is impractically low, usually averaging between 6 to 9%, or the wet and dry tenacities are extremely low, and the fibers are not adapted to working up as such or with wool fibers, on conventional textile equipment. V

The primary object of this invention is to provide cellulose-phenylthiourethane fibers, filaments, or yarns having a dry extensibility of at least 15%, a wet tenacity of at'least 0.75 gm/denier, and adry tenacity of at least 1.5 gms./denier. Another object is to provide a new and 2 of the cylinder. The flange is ground to provide a level surface, and a cellophane membrane 52 mm. in diameter and 0.022 mm. thick is placed over it. The membrane is secured in place by two Bakelite rings held together by thumb screws. Into this apparatus, there are placed 45 cc. of the spinning bath the dehydration value of which is to be measured. The apparatus is set in a 25 gallon thermoset of circulating fresh water which is kept at 50 C. and to which preheated fresh water is continually added. The liquid inside the graduate is kept at the same level as the liquid outside by lowering the graduate as the volume inside increases. The volume increase in the graduate is recorded as afunction of time. The final volume reading, which is essentially an equilibrium value, is made at the end of 168 hours. The dehydration value of the bath is defined as the percent volume increase in thegraduate in 168 hours. I

Where the dehydration value of the bath is referred" to in this application, the reference is to a bath having a dehydration value determined by the foregoing test.

The coagulating bath is buifered, has a pH between 3.2 and 6.2, and may comprise an aqueous solution of any combination of inorganic acid salts which do not form insoluble compounds with cellulose phenylthiourethane. Examples of suitable coagulating baths are aqueous solutions of mixtures of sodium sulfate and sodium phosphate, and aqueous solutions of mixtures of sodium sulnovel process for producing shaped articles, such as fibers,

filaments, yarns, films, tubes suitable for use as sausage casings, etc. of a cellulose-phenylthiourethane.

In the drawings, V V

Figure 1 is a graph illustrating physical properties of cellulose phenylthiourethane fibers obtained in accordance with the invention;

Figure 2 is a graph comparing the elongations at break of cellulose phenylthiourethane fibers obtained with various spinning baths;

Figure 3 is a graph comparing the wet tensile strengths of phenylthiourethane fibers obtained by spinning into various baths;

Figure 4 is a graph showing dry tensile strengths of cellulose phenylthiourethane fibers obtained by spinning into various baths; and

Figure 5 is a cross-sectional view 'of a typical cellulose phenylthiourethane fiber obtained in accordance with the invention.

In. accordance with the invention, 'the shapedarticles, such as fibers, filaments, and yarns, are obtained by extruding an aqueous alkaline solution of the cellulosephenylthiourethane, for example, a solution thereof in aqueous sodium hydroxide, into an aqueous coagulating bath having a pH of between 3.2 to 6.2, preferably 4.5 to 5.0, and a dehydration value of at least 215 determined as follows:

An ordinary 100 ml. graduate is provided with a hole in its bottom wall, which hole has a diameter the same as that of the graduated section. The graduate is bent at an angle'of 90 at the bottom so that the base of the graduate forms a flange parallel to the graduated walls fro fate, sodium bisulfite, and sodium borate.

In one presently preferred embodiment of the invention, the aqueous coagulating bath is generally characterized by a sulfate ion concentration of at least 7%, gen 'erally from 7 to about 11%, a phosphate ion concentration of at least 11.7%, generally from 11.7% to 18%,

and preferably from 16.5 to 17.5%, a pH between 3.2 and 6.2, preferably between 4.5 and 5 .0, and a dehydration value of at'least 215, and preferably between 215 and 26S.

The coagulating bath is maintained at, or reconverted to, a pH between 3.2 and 6.2, preferably between 4.5 and 5.0 by the addition of a controlled amount of acid, for example, sulfuric acid, phosphoric acid, or a mixture of sulfuric and phosphoric acid, when the bath contains sulfate and phosphate ions, and serves to carry hydrogen ions to the cellulose-phenylthiourethane streams for neutralizing the sodium hydroxide introduced therewith; thereby coagulating them. The coagulated filaments are withdrawn from the bath, stretched, washed, and dried.

In this preferred process, neutralization of the sodium hydroxide introduced into the coagulating bath involves the following reactions:

The coagulating bath does not contain free phosphoric acid. Any phosphoric acid added to the bath in conjunction or admixture with the sulfuric acid for controlling pH functions to reconvert dibasic sodium phosphate to monobasic sodium phosphate as follows:

the reactions illustrated is removed continuously or intermittently by Withdrawing all or a portion of the coagulating bath to a crystallizer for crystallization of Glaubers salt. Excess water is evaporated from the coagulating bath by intermittently withdrawing a portion of the bath to an evaporator, removing the water, and returning the dehydrated bath to the spinning vessel.

The coagulating bath containing sulfate and phosphate Patented Dec. 27, 1955 ions must have a combined sulfate and phosphate ion concentration of at least 18.7%, (the phosphate ion predominating) since below that value, the fibers having a dry extensibility of at least 1.5% are not obtained. Provided the lower limit for the total sulfate and phosphate ion concentration is maintained, the concentration of salt in the coagulating'bath may reach saturation.

The temperature of the coagulating bath should be between 25 and 75 C., and is preferably from 45 to 55 C.

The fibers withdrawn from the coagulating bath are preferably stretched from to 40% between godets or by means of any other suitable device, for example as they are passed over a thread-advancing, thread-stretching reel, or the like.

Cellulose-phenylthiourethanes in which the ratio of phenylthiourethaue groups to anhydroglucose units is from 1:2 to 1:5, preferably from 1:2.5 to 1:3.5 may be used in practicing the invention. For the present purposes, cellulose-phenylthiourethanes in which the phenylthiourethaue groups are substantially uniformly distributed throughout the cellulose are preferred. The production of such cellulose-phenylthiourethane is described in my copending application, Serial No. 65,742, filed December 16, 1948, now Patent No. 2,705,231.

Further details of the practice of the invention are given in the following examples.

Example 1 A spinning solution containing 8.5% of a cellulosephenylthiourethane (ratio of phenylthiourethaue groups to anhydroglucose units 1:3) was prepared by suspending the ether in water by vigorous stirring. Sodium hydroxide was dissolved in water, and the solution was chilled and a sufiicient amount thereof was added slowly, with stirring, to the cellulose-phenylthiourethane slurry, to produce a final spinning dopecontaining 3% of sodium hydroxide. The solution was filtered, deaerated and extruded through a spinneret having 40 holes each 0.0035 inch in diameter, into a coagulating bath prepared by dissolving 9000 parts by weight of sodium sulfate, 4,750 parts by weight of sodium hydroxide, and 11,500 parts by weight of 85% phosphoric acid in 34,750, parts of water. This bath contained 10.9% sulfate ion and 17% phosphate ion, and had a pH of 5 which was maintained throughout the spinning. The temperature of the bath was 55 C. The dehydration value was 265. The yarns were given an immersion of 26 inches in the coagulating bath, withdrawn from the bath, stretched 20% between godets, and collected in a box rotating at a speed of 7500 R. P. M. (spinning speed: 60 meters/minute). The yarn was washed with cold water and dried. Photomicrographs of these fibers show that they are crenulated in cross-section.

Figure 5 shows a typical cross-section of such fibers.

Example 11 Example I was repeated, except that the coagulating bath was maintained at a pH of 3.2.

Example III Example I was repeated, using a coagulating bath maintained at a pH of 4.2.

Example IV Example I was repeated, the coagulating bath being maintained at a pH of 6.2.

Example V Example I was repeated except that the coagulating bath contained 7% sulfate ion and 11.7% phosphate ion and was maintained at a pH of 4.2. The bath had a dehydration value of 215.

V I I 4 Example VI An aqueous spinning solution containing 8.5% by weight of the cellulose phenylthiourethaue and 3.0% by weight of sodium hydroxide was extruded through a spinneret having holes, each 0.0035 inch in diameter, into a coagulating bath prepared by dissolving 10% by weight of sodium bisulfite, 20% by weight of sodium sulfate, and 2% by weight of boric acid in water, and maintained at 50 C. Spinning speed: 60 meters per minute. This bath contained 7.78% bisulfite ion, 13.52% sulfate ion, and 1.98% borate ion. It had a dehydration value, determined as described above, of 243, and a pH of 4.5-5.0. After an immersion of 26 inches, the yarn was withdrawn, stretched 20%, and collected in a box rotating at 7500 R. P. M. It was reeled from the box, skeined, washed with threechanges of cold water, centrifuged, washed again with cold water, and centrifuged. The skein was allowed to dry at room temperature. It had a dry tensile strength of 1.52 gms./denier, and a wet tensile strength of 0.85 gm./den.; a dry extensibility of 18.2% and a wet extensibility of 29.8%.

Example VII A spinning solution as in Example VI was extruded into a coagulating bath prepared by dissolving 15% by weight of sodium bisulfite, 17% by weight of sodium sulfate, and 1% of boric acid, in water. This bath contained 11.67% bisulfite ion, 11.49% sulfate ion, and 0.99% borate ion. It had a dehydration value of 235 and a pH of 4.55.0. The bath was maintained at 50 C. The yarn, which was spun under the conditions of Example VI, had a dry tensile strength of 1.5 gms./den., wvet tensile strength of 0.79 gm./den.; a dry extensibility of 16.9%, wet extensibility of 28.5%.

Example VIII An aqueous spinning solution as in Example VI was extruded into a coagulating bath obtained by dissolving 10% sodium sulfate, 15% sodium tetraborate, and 15% sodium bisulfite, by weight, in water. This bath contained 6.76% sulfate ion, 11.58% tetraborate ion, and 11.67% bisulfite ion. It had a dehydration value of 250 and a pH of 4.55.0. The bath was maintained at 50 C. The yarn was given a 54 inch immersion in the bath and stretched 20%. It had a dry tensile strength of 1.53 gms./den., wet tensile strength 0.75 gm./den., dry extensibility of 17.8%, wet extensibility of 31.5%.

The fibers obtained by Examples I to VIII inclusive were crenulated in cross-section, characterized by a dry extensibility of at least 15%, and had good wet and dry tensile strengths for a cellulose-phenylthiourethaue yarn. The physical properties of the fibers obtained in Examples I to V inclusive, which were typical of the fibers produced in accordance with the invention, are illustrated in Figure 1 of the accompanying drawing, in which the dry extensibility and dry and wet tenacities are plotted against the pH of the bath.

The temperature of the coagulating bath having the controlled pH was varied to determine the effect of temperature on the wet and dry tensiles of the yarns. As will be apparent from a consideration of curve I, in Figure 2 of the drawing, yarns having a dry extensibility of 15 are obtained, using the coagulating baths of the invention, regardless of the bath temperature, and the extensibility increases with increase in the temperature of the bath. This high dry extensibility, which renders the fibers useful for general textile purposes and adapted to working up on conventional equipment, is not obtained at the expense of either wet or dry tenacity. As is shown by curve I, Figure 3 of the drawing, in which the wet tenacity is plotted against temperature, the wet tenacity is at least 0.7 5 gm./ denier and increases with temperature increase. The dry tenacity is at least 1.0 gm./denier, and also increases with increase in bath temperature, as shown 5. by curve I, in Figure 4, wherein the dry tensiles are plotted against bath temperature.

These fibers cannot be obtained using coagulating baths which do not meet the requirements of pH and dehydration value disclosed herein, as is shown by a comparison of curves II, III, IV, and V of Figure 2 with the correspondingly numbered curves of Figures III and IV.

As shown by curves II (Figures 2, 3, and 4) the fibers obtained by spinning cellulose-phenylthiourethane in 3% sodium hydroxide into 30% aqueous ammonium sulfate, had a dry extensibility above 15% at bath temperatures from 5 to 50 C., but the wet tensile strength was very low, at all temperatures, and both the wet and dry tensiles decreased sharply as the temperature increased and NH3 was liberated. No variation in the conditions resulted in fibers having both a dry extensibility of at least 15% and acceptable wet and dry tensile strengths. Ammonium sulfate solutions have the further disadvantage that the fibers are dark-colored, and that the pH is extremely diificult to control, both disadvantages being attributable to evolution of ammonia from the bath, a phenomenon which renders any ammonium salt bath uneconomical as a coagulant for the fibers and compli cates control of the pH. The fibers or yarns formed in the armnonium sulfate bath are round in cross-section and tend to cement together when they are washed with hot water after being withdrawn from the ammonium sulfate solution. 7

Fibers having a high dry extensibility, even a high extensibility coupled with low wet and dry tensiles, could not be obtained by spinning the cellulose-phenylthiourethane into other conventional coagulating baths, which did not have the pH and dehydration values of the baths of the present invention, regardless of the temperature of the bath. The fibers obtained by spinning the solution into a bath consisting of water containing 21% of di-ammonium hydrogen phosphate at 15 C. had a dry extensibility of 15% which decreased immediately with increase in the temperature (curve III, Figure 2) but the wet tenacity at 15 C. was low, and both the wet and dry tenacities fell 01f sharply at temperatures above 15 C. (Curves III, Figs. 3 and 4.) These fibers are also round in cross-section.

For purposes of further comparison, the cellulosephenylthiourethane solution was spun into a coagulating bath comprising an aqueous solution of 15 sodium bisulfite and 10% sodium sulfate at various temperatures. At a coagulating bath temperature of 25 C., the fibers obtained had a dry extensibility of about 13%, which decreased abruptly as the temperature was increased (curve IV, Fig. 2), the wet tensile rose from 0.5 gm./denier at 25 C. to about 0.65 at 45 C., and then fell oft as the temperature was increased (curve IV, Fig. 3), while the dry tenacity rose from about 0.8 gm./ denier at 25 C. to about 1.5 gms./denier at 45 C., after which it dropped. It was impossible to produce fibers having both a dry extensibility of at least 15%, and a wet tenacity of at least 0.75 gm./denier, and a dry tenacity of at least 1.5 gms./denier, by extruding the cellulose phenylthiourethane solution into the sodium bisulfitesodium sulfate bath. The fibers formed in that hath are harsh and dull and of generally poor quality. They are round in cross-section. This sodium bisulfite-sodium sulfate bath had a dehydration value of only 194, which is below the minimum required. Also, this bath was not buffered, as were the baths described in Examples VI and VII, and which contained boric acid. A well-buffered bath is required to produce the fibers of this invention.

The curves designated V in Figs. 2, 3, and 4, show the results obtained by spinning the solution of the cellulosephenylthiourethane in 3% sodium hydroxide into 30% ammonium chloride solution. At all temperatures of spinning, the dry extensibility of the fibers was less than 10%. The fibers are round in cross-section.

The fibers produced in the various baths were formed from a spinning solution as described in Examples I-VIII herein, under similar spinning conditions, and handled in the same manner as the fibers formed in the coagulating baths of the invention.

As compared to the fibers formed in theother coagulating baths, the fibers formed in accordance with the invention had, at all temperatures for the coagulating bath between 25 and C., a dry extensibility of at least 15%, a wet tensile strength of at least 0.75 gm./denier, and a dry tenacity of at least 1.5 gms./denier. As is evident from Fig. 1 and curves I of Figs. 2, 3, and 4, the optimum temperature for the bath is about 45 C., the optimum pH being about 5.2.

The crenulated cross-section of the cellulose-thicurethane fibers of the invention imparts high covering power and the capacity to absorb and retain large amounts of moisture to fabrics comprising them. The water-retention capacity of the crenulated fibers formed in accordance with the invention varies between 52.4% at a bath temperature of 45 C., and 58% at a bath temperature of 55 C. The round fibers formed in the other baths illustrated herein for comparison purposes, and which do not have a pH value between 3.2 to 6.2 and a dehydration value of between 215 and 265, have a water-retention capacity which varies between 41.7% at a temperature of 45 C. and 51.5% at a bath temperature of 55 C.

Although the water-retention capacity of the crenulated fibers of the invention is higher than that of the round fibers, the cross-sectional swelling of the crenulated fibers compares favorably with the cross-sectional swelling of the round fibers, on exposure to moisture. The crosssectional swelling of the round fibers varies between 20.4 and 25.4%, and the crosssectional swelling of the crenulated fibers formed in accordance with this invention varies between 20.3 and 25.1%.

The linear swellings also compare favorably. Thus, the linear swelling of the best fiber which can be obtained using an ammonium sulfate coagulating bath is 1.42.0%, while the linear swelling of the fibers produced in accordance with the invention is 1.4l.8%.

The invention provides, for the first time, cellulosephenylthiourethane fibers having a dry extensibility of at least 15%, which are resilient, characterized by good wet and dry tenacities, and adapted to working up on conventional textile equipment either alone or in blends with wool fibers for which latter purpose they are particularly well suited because of their crenulated cross-section and consequent high water-retention capacity, coupled with low cross-sectional and linear swelling in the presence of moisture. Fabrics formed from these fibers or from blends thereof with wool fibers have increased voluminosity, high covering power, and a pleasing hand or feel. The cellulose-phenylthiourethane fibers are resistant to organic solvents, micro-organisms and moths, and more resistant to acids than cellulose fibers, and since they are non-thermoplastic, they can be ironed at elevated temperatures without matting down and becoming boardy. The fibers accept wool dyes and mixtures thereof with wool fibers can be dyed in the same dyebath. The fibers burn but do not support a flame, have a high drying rate, and shed soil easily, this latter property being desirable in a fiber intended for blending with wool. The electrostatic properties of the cellulose-phenylthiourethane fibers are similar to those of silk and wool.

Since variations and modifications may be made in carrying out the invention, without departing from its spirit and scope, it is to be understood that the invention is not to be limited except as defined in the appended claims.

I claim:

1. Fibers of a cellulose-phenylthiourethane in which the ratio of phenylthiourethane groups to anhydroglucose units is from 1:2 to 1:5, said fibers being crenulated in cross-section, and having a dry elongation at break of at least 15%, a wet tenacity .of at least 0.75 gm./denier, and a dry tenacity of at least 1.5 gins/denier.

2. The method of producing ,crenulated fibersv of a cellulose phenylthiourethane having a dry extensibility of at least 15%, a wet tenacity of at least 0.75 gm./ denier, and a dry tenacity of at least 1.5 grns./ denier, which comprises extruding a dilute aqueous alkaline solution of a cellulose thiourethane in which the phenylthiourethane groups are substantially uniformly distributed in a ratio of from one phenylthiourethane group per two anhydroglucose units to one phenylthiourethane group per five anhydroglucose units into an aqueous coagulating bath maintained at a temperature between 25 C. and 75 C. and characterized by a sulfate ion concentration between 7% and 11% and a phosphate ion concentration between 11.7% and 18%, the bath having a buffered pH between 3.2 and 6.2 and a dehydration value between 215 and 265, withdrawing the fibers thus formed from the bath, stretching the fibers, washing the fibers and drying the fibers.

3. A method as in claim 2 in which the fibers are washed with cold water.

4. A method as in claim 2 in which the coagulating bath has a pH between 4.5 and 5.0.

5. A method as in claim 2 in which the coagulating bath contains 7% sulfate ion and 11.7% phosphate ion. '6. A method as in claim 2 in which the coagulating bath contains 10.9% sulfate ion and 17% phosphate ion.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Latest Survey of. New Synthetic Fibers by William D. Appel January 1945, pages 2882.

Artificial Silk Reinthaler D. Van Nostrand Company Incorporated 1928 New York, pages 124 to 125. 

2. THE METHOD OF PRODUCING CRENULATED FIBERS OF A CELLULOSE PHENYLTHIOURETHANE HAVING A DRY EXTENSIBILITY OF AT LEAST 15%, A WET TENACITY OF AT LEAST 0.75 GM./DENER, AND A DRY TENACITY OF AT LEAST 1.5 GMS./DENIER, WHICH COMPRISES EXTRUDING A DILUTE AQUEOUS ALKALINE SOLUTION OF A CELLULOSE THIOURETHANE IN WHICH THE PHENYLTHIOURETHANE GROUPS ARE SUBSTANTIALLY UNIFORMLY DISTRIBUTED IN A RATIO OF FROM ONE PHENYLTHIOURETHANE GROUP PER TWO ANHYDROGLUCOSE UNITS TO ONE PHENYLTHIOURETHANE GROUP PER FIVE ANHYDROGLUCOSE UNITS INTO AN AQUEOUS COAGULATING BATH MAINTAINED AT A TEMPERATURE BETWEEN 25*C. AND 75*C. AND CHARACTERIZED BY A SULFATE ION CONCENTRATION BETWEEN 7% AND 11% AND A PHOSPHATE ION CONCENTRATION BETWEEN 11.7% AND 18%, THE BATH HAVING A BUFFERED PH BETWEEN 3.2 AND 6.2 AND A DEHYDRATION VALUE BETWEEN 215 AND 265, WITHDRAWING THE FIBERS THUS FORMED FROM THE BATH, STRETCHING THE FIBERS, WASHING THE FIBERS AND DRYING THE FIBERS. 